Motor vehicle electrical control systems control the electrical energy provided to electric energy consumption units in a motor vehicle. The consumption units include servo pumps, fuel pumps, fan motors, and lamps for the headlights, sidelights, and indicator lights. A typical control system includes a microcomputer which influences output amplifiers associated with the consumption units to vary the electrical energy provided to the units by the output amplifiers. In so doing, it is important that the consumption units and the output amplifiers connected thereto are protected from being overloaded.
To protect the consumption units from being overloaded, protective circuits have been connected directly to semiconductor output amplifiers to measure the voltage and current of the electrical energy provided to the consumption units by the output amplifiers and the temperature of the heat generated by the output amplifiers. In effect, the semiconductor output amplifier simultaneously performs safety functions.
Output amplifiers of this type are, however, quite cost intensive and have only a relatively limited use as far as their safety characteristics are concerned.